Living cells (for example, sperm, ovum, and the like) of mammals are cryopreserved. The cryopreservation of the living cells enables the preservation of hereditary resources of a specified system and kind and is effective for maintaining animal species standing on the verge of extinction and useful for human infertility treatment.
A method of freezing the ovary is disclosed in Japanese Patent Application Laid-Open Publication No. 2003-284546 (patent document 1). The ovary freezing method is characterized in that a reproductive tissue including at least the ovary taken out from a female individual of an impersonal mammal is preserved at 15 to zero degrees C. and thereafter frozen by a vitrification method.
As a method for freezing mammalian embryos, as disclosed in a patent document 1 (Japanese Patent Application Laid-Open Publication 2000-189155), there is proposed a method for freezing and storing mammalian embryos that mammalian embryos or ova are bonded to the inner surface of the freezing and storing container such as the sterilized frozen straw, frozen vial or frozen tube by using a vitrified liquid in an amount minimum and enough to enclose the mammalian embryos or the ova therewith. The freezing and storing container is sealed and rapidly cooled by bringing the freezing and storing container into contact with liquid nitrogen. In the thawing method, the freezing and storing container stored in the above method is taken out of the liquid nitrogen and one end thereof is opened. A diluted liquid of 33 to 39 degree C. is injected directly into the container to thaw the mammalian embryos or the ova and dilute the vitrified liquid. This method eliminates a possibility that the mammalian embryos or the ova are infected with a disease through viruses or bacteria and is capable of storing them at a high survival rate and thawing them and diluting the vitrified liquid.
The present applicant proposed the tissue piece cryopreserving plate as disclosed in Japanese Patent Application Laid-Open Publication No. 2008-222640 (patent document 3). The tissue piece cryopreserving plate is the plate-shaped metal member which has the width equal to or a little larger than the predetermined width of the cutting portion-specifying open portion, is extendable at a predetermined length, allows the tissue piece cut off from a living tissue bye using the tissue cutting position-specifying tool to be placed thereon, and has a large number of holes.
The present applicant proposed the cryopreserving tool as disclosed in Japanese Patent Application Laid-Open Publication No. 2012-219017 (patent document 4). The cryopreserving tool of the patent document 4 is used to freeze a biospecimen such as a tissue piece, a cell, and the like by means of a vitrification freezing method (rapid vitrification freezing method and super-rapid vitrification freezing method). The cryopreserving tool has the specimen placing part including the stainless sheet and the holding part fixed to the proximal end portion of the specimen placing part. The cryopreserving tool does not have a through-hole in the region of the specimen placing part where the biospecimen is to be placed, but the stainless sheet is used as the specimen placing part.